1. Field of the Invention
The present invention relates to a goods-handling door of the type having a raisable curtain that comprises a deformable insulating curtain. Such doors are to be found in industrial premises, where they serve to keep different spaces apart in factories or in warehouses. There exist systems for raising the curtains in such doors quickly (by folding them up concertina-like or by winding them up), thereby enabling vehicles to pass through the doors without being significantly slowed down.
2. Description of Prior Art
In such an application, it is important to be able to see through the curtain so as to avoid collisions between vehicles moving towards the door from opposite sides. Simultaneously the curtain is required to provide good insulation, both thermally and acoustically.
European patent EP 0 076 349 discloses a door curtain that satisfies those two requirements. It is made up of two transparent flexible skins that are held together in spaced-apart regions, thereby defining pockets between them. The various pockets are filled with strips of insulating material such as polyurethane foam. The strips are pierced by holes to provide a degree of visibility.
That type of curtain suffers from a drawback that stems from the mechanical properties of foam. The foam is not mechanically strong and it becomes compacted within the pockets under the effect of its own weight. To remedy that problem, it is the practice to use panels of foam that extend over the entire curtain. The two skins disposed on either side are then pinched together in spaced-apart regions, thereby obtaining a kind of quilting effect.
Other known curtains suffer in turn from a drawback that stems from the mechanical properties of foam. This time it is the poor ability of foam to withstand repeated deformation that presents difficulties. Goods-handling doors of the kind described are designed to open and close often, e.g., in the range 100 to 1,000 times per day. As a result, the foam, which is folded or bent on numerous occasions, very quickly starts to tear. This happens in particular around the bridges left between the visibility holes or at the places where the skins are pinched together. The appearance of a door is quickly spoiled in this way.
The problem which arises is that of finding an insulating deformable curtain that has better endurance than prior art curtains. It must also be compatible with visibility requirements.